Aging and postural control. A comparison of spontaneous- and induced-sway balance tests.
Two different balance testing methods were compared: (1) measurement of spontaneous postural sway during quiet standing, and (2) measurement of induced postural sway in response to an applied postural perturbation. Eyes-open tests were performed in 64 healthy young and elderly adults and in five elderly subjects with a history of falling. In both balance tests, the sway was defined in terms of the displacement of the center of pressure on the feet. Spontaneous sway was quantified using a number of different amplitude- and frequency-based parameters. Induced sway was measured in response to anterior-posterior acceleration of a platform on which the subject stood. The induced-sway test was specially designed to be safe and nonthreatening for elderly subjects; thus, the platform perturbation was confined to small accelerations and a gentle pseudorandom motion was used. To derive a measure of postural stability, the data from this test were fitted with a model that was then used to predict the response to sudden (transient) perturbations, thereby simulating the response in actual falls. Although both induced- and spontaneous-sway measures demonstrated significant aging-related decreases in stability, the differences were more pronounced for the induced-sway data. Conversely, some of the spontaneous-sway measures were much more successful in distinguishing the fallers from the nonfallers. There was a significant correlation between induced-sway and certain spontaneous-sway measures in the normal young adults; however, in the elderly normals and fallers, the data from the two types of balance tests either showed no correlation or, for certain spontaneous-sway measures, tended to show an inverse relationship.
Maki
B E
BE
Centre for Studies in Aging, Sunnybrook Medical Centre, Toronto, Ontario, Canada.
Holliday
P J
PJ
Fernie
G R
GR
D000054:Acceleration / Q000009:adverse effects; D000057:Accident Proneness; D000058:Accidental Falls / Q000517:prevention & control; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait / Q000502:physiology; D006801:Humans; D007699:Kinesthesis / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*